Meetings held in large rooms involving two or more individuals can be facilitated using a room audio system, or, in the case that individuals are conducting a remote meeting, an audio conferencing system can be used. Room audio systems or audio conferencing systems typically include some number of microphones, at least one loudspeaker and a base station which may or may not be linked to a network. In a room audio system, microphones can operate to pick up acoustic audio signals (speech) and transmit the signals to a base station which generally operates to provide session control and to process the audio signals in a number of ways before sending it to a loudspeaker located in the room to be played. Among other things, the base station can be configured to amplify audio signals, it can regulate signal gain and suppress noise, and it can remove acoustic echo from signals received by the microphones.
FIG. 1 is a diagram showing functional elements comprising a commercially available room audio system 100. The system 100 can be comprised of a number of wireless microphones 11 and/or wired microphones 12, one or more loudspeakers 13, and an audio control and processing device 14. Typically, in such room audio systems, the loudspeakers 13 are wired to the device 14 and positioned within the room so that all of the individuals in the room can easily hear what each of the other individuals in the room is saying, and the processing device 14 includes complex digital signal processing and audio signal control functionality. Depending upon its capability, the processing device 14 can be a relatively expensive element of the overall system cost. Including a separate device 14 in each room in which an audio system is installed can be expensive.
A commercially available audio conferencing system 20 illustrated in FIG. 2 is comprised of some number of wired or wireless microphones 21 and loudspeakers 22 associated with an audio control and processing device 23 (such as a base station) which is in communication with one or more audio sources (can be local or remote, far end sources) over either a local or a wide area network. In addition to having audio session control functionality such as audio channel mixing, amplification and gain control, the device 23 can also have functionality for removing feedback and acoustic echo from the microphone signals. High quality audio is facilitated in such an audio conferencing system having multiple, wireless microphones attached to an individual which allows the individual to move around a room with the microphone during a conferencing session. As with conferencing system 100 described earlier with reference to FIG. 1, a separate processing device 23 is included in each room in which the system is installed and is typically the most expensive part of the system.
Another audio conferencing system 300 configuration is shown with reference to FIG. 3 in which each of a plurality of separate conference phones (31A-31Z) have an integrated microphone, loudspeaker, control and handset. Each of the phones are shown to be connected over a local network 32 to a common audio processing device 33. In this configuration, all of the audio signal processing is performed by a digital signal processor (DSP) 34 comprising the device 33. In order for a system in this configuration to perform acoustic echo cancellation (AEC), it is necessary that the timing of an audio sampling function at each of the phones and at the DSP 34 be tightly correlated or synchronized. Having the signal processing functionality located in a single, network device as opposed to including this functionality in each of the conference phone simplifies the operation and lowers the cost of each phone. While the system 300 in FIG. 3 is reasonably priced, it is not well suited for a large meeting room or conference room application in which there are many individuals spread out in the room or in which the individuals are moving around the room.